The present invention relates to servicing of the brakes on large trucks, primarily tractor-trailer configurations. It provides a convenient tool for the disassembly and reassembly of the wheel-mounted portion of the brake mechanism when the unit must be serviced
A typical configuration for truck/trailer air brakes is a pair of approximately semi-circular components called “shoes,” each contacting half of a circular brake drum surrounding the axle of the vehicle. Brake pads, which may be metal or ceramic composites designed to withstand the heat and pressure of substantial friction, are attached to the outer surface of the shoes. When a brake pedal is depressed, a compressed air delivery network causes a cam to turn, which pushes the brake shoes outward, causing the pad to frictionally engage the surrounding drum as it rotates, slowing its motion to a stop.
The brake shoes are attached to a spider, a round plate on the end of the axle, by anchor pins or other components. The brake shoes are movably secured to each other by springs, so that after the brake pedal is released, the shoes and pads withdraw from contact with the drums. Most brake assemblies have one or two retainer springs on one side of the axle and a return spring on the side of the axle adjacent the cam. The return spring must quickly pull the shoe away from the drum when the brake is released, and such springs are very strong, often 100 lb tension or more. When truck brakes are serviced, the shoes must be removed to replace the pads, and this entails stretching the retainer and return springs to remove them from their anchor positions. These springs are usually replaced as part of the service. The return spring, in particular, is difficult to stretch, and service personnel must find a way to carefully apply leverage to accomplish this. When standard tools, such as screwdrivers, pry bars or pliers are used, frustration and injuries can result as the spring slips from the tool.